Catheterization procedures are well known for diagnosis and therapy of lesions in the cardiovascular system. One such procedure is angioplasty which reduces the damaging effects of vascular plaque blockage or constriction in blood vessels.
In an angioplasty procedure, an expandable balloon is introduced into the patient's arterial system and advanced until it is positioned in the region of the blockage or constriction. Once so positioned, the balloon is expanded by filling it with a liquid. In successful procedures, the expandable balloon presses outwardly against the walls of the artery and expands the artery to a degree to which the artery is either partially or totally re-opened to blood flow.
A typical angioplasty procedure, and components used in practicing the procedure, are now described.
Prior to initiating the angioplasty procedure, a guiding catheter is placed typically via the femoral artery into the aorta and its tip is engaged into the coronary arteries which branch from the aorta. This entrance into the coronary artery is called the ostium. Once placed, the guiding catheter acts as a conduit to access the coronary arteries with a balloon guidewire and balloon catheter. The guiding catheter is a portion of plastic tubing having a length of about 95 centimeters, an inside diameter of about 0.08 inches, and an outside diameter of about 2.5 millimeters.
The physician positions a balloon catheter within the patient with the aid of a guidewire. The guidewire is a piece of elongated wire, approximately 175 centimeters in length, and about 0.010-0.018 inches in diameter. The distal tip of the guidewire can be shaped to form a "J" configuration. This "J" shape allows the physician to steer the wire by twisting the proximal extremity of the guidewire while advancing or retracting the guidewire.
The balloon catheter is an elongated flexible member having a balloon located near its distal end. In a so called "Over-the-Wire" catheter system one longitudinal opening through the catheter defines a sleeve through which the balloon guidewire can be passed. A second longitudinal passage in the catheter defines a conduit communicating with the interior of the balloon and through which inflation fluid can be injected to inflate the balloon.
Among the types of balloon catheters is one of a type in which the two longitudinal passages are generally side by side and parallel. In another type of balloon catheter, the two longitudinal passages are co-axial. In this latter type, the balloon guidewire is passed down the inner passage and the inflation fluid is injected into the balloon via the outer passage.
Balloon catheters, as well as associated apparatus and method for use in angioplasty, are described in U.S. Pat. No. 5,040,548, issued on Aug. 20, 1991, to Yock, and U.S. Pat. No. 4,762,129, issued on Aug. 8, 1988. Each of these issued U.S. patents is hereby expressly incorporated by reference.
Using the over-the-wire insertion technique, the physician passes the balloon guidewire through the guidewire passage in the balloon catheter, leaving a portion of the balloon guidewire extending from the distal end of the balloon catheter and also a portion extending from its proximal end.
This assembly is then inserted into the proximal end of the guiding catheter, distal end first. The assembly is inserted until the balloon which is attached near the distal end of the balloon catheter is near the distal end of the guiding catheter. At this point, the physician, while maintaining the balloon catheter stationary, pushes on the balloon guidewire to advance it outwardly from the distal end of the guiding catheter.
The balloon guidewire can be steered by appropriate twisting movement by the physician. The physician steers the guidewire into the chosen one of the coronary arteries, and advances it until it reaches a location of constriction which the physician desires to re-open. Carefully, the physician eases the guidewire through the region of restriction until a portion of the guidewire is on the opposite side of the constriction, relative to the guiding catheter.
With the balloon guidewire held stationary, the physician then advances the balloon catheter. The distal end of the balloon catheter, as it is advanced, will, of course, follow the balloon guidewire which is already in place.
The physician continues to advance the balloon until it is located in the region of constriction of the artery. With the balloon and its associated catheter held stationary, inflation fluid is injected into the conduit which communicates with the balloon, causing it to inflate. Inflation of the balloon expands the walls of the artery in the region of constriction and, in successful procedures, re-opens the artery to sufficient blood flow.
Arteries vary in size, and therefore balloon catheters having balloons of different sizes are provided for the physician's selection. These balloons, when inflated, range from about 1.5 millimeters to about 4 millimeters in diameter.
Sometimes, it is necessary for the physician to use more than one balloon to open an artery. Sometimes, the chosen balloon is too large to be advanced into the constricted area. In other instances, the first chosen balloon size, even when inflated, is not large enough to open the constricted area to the degree desired. In such cases, it is necessary to exchange one balloon for another during the same angioplasty procedure.
In order to accomplish this exchange, the guidewire is left in place, and the balloon catheter is withdrawn entirely from the guiding catheter until it is completely disengaged from the guidewire. A new balloon catheter, having a different sized balloon, is then re-inserted over the guidewire and advanced back to the location of the constricted area, where it is used to effect the desired result.
Once the guidewire has been inserted through the constricted area, it is desirable to leave the guidewire in place for the entire angioplasty procedure; even during exchanges of balloons. The reason for this is that, when a foreign object, such as the guidewire, is introduced into an artery, the artery walls sometimes go into spasm, and constrict generally along a substantial portion of its length. If the artery tends to contract in this way, removal of the guidewire while the artery is so contracted will sometimes render it virtually impossible to re-insert the guidewire through the contracted artery.
Additional prior art patents relating to balloon catheters are U.S. Pat. No. 4,762,129 to Bonzel, U.S. Pat. No. 5,098,381 to Schneider, U.S. Pat. No. 5,049,132 to Shaffer et al, and U.S. Pat. No. 5,315,747 to Solar and published PCT applications WO 92/17236 to Tartaglino et al and WO 92/20397 to Jung.
The Bonzel '381 patent concerns a so-called "rapid exchange" guidewire arrangement. Using such an arrangement the guidewire can be inserted and properly positioned before the catheter is inserted into the guide catheter.
It is a general object of the present invention to provide apparatus and method for facilitating introduction and exchange of balloons in angioplasty procedures.